1. Field of the Invention
The present invention pertains generally to viscous product dispensing systems. More particularly, the invention pertains to product dispensers that eliminate residual product leakage from the dispenser (commonly known as the “drool effect”) after the actual amount of product that is desired by the user has been dispensed. Additionally, the invention relieves residual pressure within the dispenser which helps reduce product degradation caused by ingredient separation.
2. Description of Related Art
Systems for dispensing viscous flowable materials such as soft-solid deodorant/antiperspirant products, are well-known in the prior art. Typically, the product is extruded out of a container via a plurality of openings that are located at the top of the container. To do this, a chamber in the interior of a dispenser is loaded with the desired product. The product is supported by an underlying structure, such as a platform, piston or elevator. The user manipulates a thumbwheel or a slider which moves the underlying structure toward the top of the container. This action causes the product to be expelled out through the top openings.
One of the inherent problems with the prior art devices is that moving the underlying structure toward the top of the container, decreases the volume of the interior chamber. This pressurizes the product, which causes an additional small amount of product to be expelled through the openings, even after the user has already dispensed the desired amount of product and the user has stopped moving the underlying structure toward the top of the container. The result is a slight oozing, or weeping, of product out of the container top openings (known as the “drool” effect). The drool effect is undesirable in the liquid dispenser manufacturing industry, and it is desired to produce a viscous product dispenser that eliminates this effect. Moreover, the elimination of residual pressure on the product, will inhibit product degradation caused by ingredient separation. This most commonly occurs in fluid and fluid solid multiple component mixtures.
U.S. Pat. No. 5,540,361, which issued to Fattori for an invention entitled “Cream Deodorant Dispenser,” discloses an elevator cup 11 with a spring element 12 which extends into a first portion and into a second portion of the elevator cup. Differential flexing between the first portion and the second portion during dispensing of the product results in a retracting force that slightly withdraws the elevator cup when dispensing is stopped.
A problem with the Fattori device is that the first portion, second portion and spring element are a continuous structure. This produces an unpredictable diaphragm-like action resulting in erratic movement of the elevator cup.
U.S. Pat. No. 5,879,096, which issued to Franta et al. for an invention entitled “Gel/Cream Applicator,” discloses an intermittently rotatable spindle with threads having discrete valleys on their upper surfaces. Pins from an elevator follow the upper surfaces during rotation of the spindle. The elevator slightly retracts to prevent product drool, whenever the pins move into the valleys.
The problem with the Franta et al. device is the upper surface valleys provide the same amount of retraction no matter what amount the fluid is pressurized. Therefore, the device does not always compensate for variations in fluid pressure, and unwanted leakage can occur.
In light of the above, it is an object of the present invention to provide a dispenser for viscous products that eliminates residual pressure on the product. It is another object of the present invention to provide a dispenser wherein product leakage is prevented when the user stops extruding product from the container. Another object of the present invention to provide a dispenser wherein the user easily manipulates the dispenser to distribute product. Yet another object of the present invention is to provide a dispenser with as few moving parts as possible for increased reliability of operation. Another object of the present invention is to provide a dispenser that is easy to assemble and manufacture in a cost-effective manner.